Method of refining waxy mineral lubricating oils



Patented July 9, 1940 PATENT OFFICE METHOD OF REFINING WAXYlVIINERAL' LUBRICATING OILS Erich Saegebarth, Long Island City, N. Y., assignor to Edeleanu Gesellschaft, m. b. H., a corporation of Germany No Drawing. Application October 6, 1934,

Serial No. 747,234

I Claims. ((1196-18) This invention relates to refining methods applicable to lubricating oil stocks containing considerable amounts of paraifines with or without aromatic and unsaturated hydrocarbons and aims 5 to produce a low pour point oil of good: color,

high A. P. I. gravity and good viscosity-temperature characteristics suitable for all uses demanding high quality.

H An object of the invention is to remove wax from lubricating oils by the filtration method, the

process being characterized by'only a small difference between temperature of filtration and pour point of the dewaxed oil obtained.

A further object of the invention is to combine the solvent extraction and dewaxing treatments for refining lubricating stocks containing aromatic and unsaturated hydrocarbons, thereby effecting a saving in equipment and operating costs.

Among the advantages secured by the invention as compared with prior methods are better operating conditions and faster filter rates in separating the wax from the oil, a larger yield of refined oil of good quality, a lower pour point for the same temperature of treatment, and a wider range of effective action upon the different kinds and grades of lubricating oil stocks such that the total distillate may be treated simultaneously by the same mode of treatment without the necessity as heretofore of fractionating.

In dewaxing mineral oil fractions, naphtha has heretofore been used asa diluent for light oils in order to reduce the viscosity sufiiciently to permit of filtration of the precipitated crystalline wax, or, for heavy oils, to increase the difference in gravity of the Wax and the oil such that the amorphous wax can be removed by centrifuging, but this does not permit treating both light and heavy fractions so as to remove the wax thereby produced by a simple filtering operation, sincethe wax from the heavy oil cannot be removed by filtering.

I have found that a mixture of benzol and liquefied sulphur-dioxide in proper proportions is more advantageous for dewaxing'than naphtha both when used with and without a filter aid, such as diatomaceous earth, for example, the pour point being much lower when; the,benzol-" S02 mixture is used than when naphtha is used under similar conditions of treatment at the same filtration temperature, and all of the wax from both heavy and light fractions can be removed by filtration, s0 fractionation is not-necessary and a total distillate can .be treated by a single operatlon. Y

.The following examples, which were carried out under identical conditions of application, may be taken as illustrative.

Example 1 5 A wax-containing Mid-Continent stock of 24.4 A. El. I. gravity and 61 S. U. viscosity at 210 F., havlng a pour point of +100 F., was treated with four times its volume of a mixture containing parts of benzol and 20 parts of S02 30 I by volume plus three pounds of diatomaceous earth per gallon of stock and filtered at 20 F. in a pressure filter, in which the pressure was kept low in the beginning and later on was gradually increased up to 30-40 pounds per square inch. 5

A dewaxed oil was obtained having an A. P. I. gravity of 23.2 and a pour point sluggish at -5 F. The yield of dewaxed oil amounted to '75 Volume percent without washing the filter cake.

Example 2 20 The same stock was treated with naphtha in dilution 1:4 plus three pounds of diatomaceous earth per gallon of stock and filtered at 20 F. under the same conditions as in Example 1.

A filtrate was obtained, which after removal of the naphtha by distillation, had an A. P. I. gravity of 23.0 and a pour point of +20 F. The yield of dewaxed oil amounted to 71 volume percent without washing the cake.

Example 3 a The treatment of Example 1 was repeated but without the use of diatomaceous earth. The de- 35 waxed oil had an A. .P. I. gravity of 23.0 and a pour point below 5 F.

Example 4 a of naphtha such filter aid is indispensable. It is further seen that benzol-S02 dewaxing produces 50 a pour point which lies 10 to 15 F. above the filtration temperature, whereas this difference amounts to as much as 40 to F. when naphtha is employed. I

The following Examples 5 and 6 may serve to stocks.

illustrate the good filter rates obtainable in dewaxing with benzol-SOz:

Example 5 The same Mid-Continent stock of 61 S. U. viscosity at 210 F. (as used in Examples 1-4) was dissolved in four times its volume of benzol-SOz :20, was cooled to 20 F. and was filtered in a filter press. The pressure did not exceed 20 pounds per square inch above normal.

The filter rate amounted to 0.5 gallons solvent free oil per hour per square foot. The dewaxed oil had the following characteristics:

A. P. I 22.8 S. U. vis. at 210 F 62 Pour F 10 Example 6 The treatment in Example 5 was repeated but with the addition of one-half pound diatomaceous earth per gallon of stock.

The filter rate amounted to 2v gallons solvent free, dewaxed oil per hour per square foot filtering area. The dewaxed oil had the same specifications as the one shown in Example 5, namely:

A. P. I 22.8 S. U. vis. at 210 F 62 Pour F --10 Example 7 shows an experiment on a different Mid-Continent lubricating oil stock. This stock, having an A. P. I. gravity of 26.1 and pour point of F., was diluted with four times its volume of a mixture of four parts of benzol and one part of liquified sulphur dioxide, and filtered at 5 F. producing a wax free oil with A. P. I. gravity of 24.7 and pour point of +10 F.

The proportion of dilution is, of course, not restricted to 1:4 (oil to diluent). Example 8 is an illustration that good results may be secured by using for instance a ratio of 1:2. Still less solvent is applicable in certain cases (mainly in handling oils of low viscosity and/or low wax content) and likewise more than 400% diluent, for instance a 1:6 ratio of oil to diluent, may be advisable in dewaxing heavy oils which contain an especially high percentage of Wax.

Example 8 The treatment of Example 1 was repeated except that the dilution with benZOl-SOz was 1:2 (oil to diluent). The dewaxed oil had 23.0 A. P. I. gravity and pour point below 5 F. The yield of dewaxed oil amounted to 60 volume percent in one pass through the filter, that is without Washing the cake.

The proportion of benzol and S02 is, moreover, not limited to the above 80:20 volume percent composition; the proportion, to be selected, depends on the type of stock and on the filtration temperature. It is only necessary to choose such benzol-SOz blends that no separation into two layers or crystallization of benzol occurs.

Itis known that the homologues of benzol act much the same way as benzol when used in conjunction with selective solvents for extracting oil I have found that these homologues are also of value in dewaxing, and where benzol is mentioned in the description and in the claims, it is understood that toluol and kindred solvents ior oil, and which are miscible with liquid S02 in the proportions used, are intended to be included.

Example 9 In the following example a blend of 300 percent toluol-SOz 70:30 was employed as dewaxing medium for a heavy East Texas overhead stock:

Stock dewaxed with 300 Untreated vol. percent stock toluol-SO.

at 20 F.

A. P.I 22.2 17.2 S. U. Vis. at 210 F 113 182 Viscosity index..- 30 Pour F +30 The above pour point of +30 F. is a viscous pour,

which upon solvent extraction was reduced to 05 F.

Also it is to be understood that the described dewaxing method is not limited to untreated stocks, but applies also to refined oils, provided that such proportions are. used that separation into two layers or crystallization of benzol does not occur, or-if so-that some other suitable solvent of low pour point miscible with the mixture in the proportion used (such as sulphur dioxide extract, gasoline, ether or chloroform etc.) be added to the mixture. Such auxiliary solvent may be removed from the filtered product by any conventional method, for instance by distillation or by addition. of liquid-S02 sufiicient to form an extract layer.

The bBDZOl-SOz dewaxing method is especially advantageous in connection with l the S02 or benzol-SOz extraction process for economical and practical reasons, but may also be applied in all other cases where removal of wax alone is to be effected.

The advantage of combined extracting andde- Waxing is illustrated by the following example of results obtained upon the same stock as in Example 1 above in which the stock was first extracted with a'mixture of benzol and liquified S02 30:70 at 32 F. followed by dewaxing withv benzol-SOz by merely adding the desired amounts of benzol and liquified $02 to the rafiinate solu-.

tion to increase the solution to 400 volume percent (based on rafiinate) 80:20 benzol-SOz.

In the above example the percentage of benzol- S02 used for extraction (column 2) is based on the untreated charge and the percentage of benzol-SOz dilution for dewaxing is based on the waxy raflinate. The rafiinate yield in the extraction process amounted to 73.4 volume precent (of untreated stock) and the yield in dewaxing was 73.0 volume percent of the waxy raifinate produced. This dewaxing yield of '73 volume per cent was obtained in one filtration without washing the filter cake. The filter rate in. dewaxing was 1.98 "gallons solvent From the foregoing results it is apparent that there is a saving in the cost of refrigeration due to the comparatively low-"temperature of the rafilnate when subjected to the dewaxing'treatment and also a saving in solvents used'due to the benzol-SO2 mixture in the ramnate solution, amounting to over 20 percent, which does not have to be evaporated from the raflinate solution and recovered until it has served its purpose in the dewaxing treatment. Moreoverit is'evident that a considerable saving in equipment is effected because the entire solvent recovery system for the rafiinate solution can be eliminated.

Example 11 shows a similar dewaxing experi ment on the waxy rafiin'ate given in Example 10. In this case the dewaxing was carried out at 20 F. without the use of filter aid. Again 400 volume percent diluent -(Benzol-'SO2) of 80:20 composition were used. A dewaxed oil with F. pour point was obtained.

Example 12 In another experiment the waxy raffinate of the 61 vis. stock was dilutedwith four times its volume of a mixture of toluol-S02 in the proportions of 80 parts toluol and 20 parts S02. Three pounds of diatomaceous earth per gallon of raffinate were added, the mixture was chilled to F. and filtered under the same conditions as above. A dewaxed oil with +5 F. pour point was obtained. The filter rate was 1.96 gallons wax free and solvent free oil per hour per square foot.

The proportions of benzol and S02 in the diluent mixture may vary, depending upon the stock and temperature of treatment. Between to 30 percent by volume of S02 in the mixture represents the usual dewaxing mixture for satisfactory operation upon medium and heavy lubricating oils at temperatures down to F.; and from 50 to '70 or 80 percent S02 is found advantageous in most instances for satisfactory extraction, but these proportions may be varied depending upon the yield, pour point and other characteristics desired, the greater the proportion of S02 the greater the selectivity and the higher the yield.

Example 13 The following table shows the results of extracting at 14 F. a Mid-Continent high pour point neutral lubricating oil stock with 400 perthe proportions of 80 parts of benzol and 20 parts of S02. The amount of wax free oil obtained was 82 percent of the volume of raffinate treated. The filter rate was 3.4 gallons dewaxed, solventfree oil per hour per square foot.

The order of treatment may be either dewaxing centration than the untreated oil has.

:followed'by extracting, or the reverse order, extracting followed by dewaxing. -'I'he' order of the steps depends mainly on the overall economics, and also to a certain extent on the character of the stock. For example, a stock containing as much as 15 to 20 percent wax may sometimes cause inconvenience in solvent extraction and in that case the dewaxing may be carried out prior to solvent extraction. More- "over, solvent extraction of a waxy stock naturally produces a rafiinate with a higher wax con- Oil with higher wax concentrations will cause higher oil losses in the dewaxing step than oils with alowwax content, unless the filter cakes produced are submitted to a more thorough washing procedure,

which, however, increases the cost.

In case the dewaxing is effected before the extracting, the cold wax-free filtrate containing substantially all of the diluent may be diluted with an additional quantity of liquid sulfur dioxide or other selective solvent until separation into a raifinate and an extract phase is obtained. It is often advantageous to use a larger quantity of liquid sulfur dioxide, depending upon the raffinate yield and quality desired. The more liquid sulfur dioxide used, the smaller the proportion of benzol in the mixture and .theless powerful the solvent becomes. Further treatment of the raffinate phase by the addition of liquid sulfur dioxide or other selective solvent to improve the quality or yield or refined oil may be resorted to if desired.

The invention enables substantial improvement to be made in the refining of waxy oils heretofore found difiicult to treat satisfactorily at reasonable cost, and is applicable to a wide variety of oils and range of products. I

My invention is not restricted to the examples given. What I claim and desire to secure is as follows:

1. A method of producing a lubricating oil of high viscosity index and low pour point from a wax bearing mineral lubricating oil, which comprises extracting the wax bearingv oil with a mixture of liquid sulphur dioxide and benzol in which the sulphur dioxide is in excess of 50 percent, in order to obtain a rafiinate phase and an extract phase, separating the two phases from each other and adding to the raffinate phase additional liquid sulphur dioxide and benzolin such amounts that the total solvent in the mixture equals at least the amount of rafiinate oil, the liquid sulphur dioxide in the solvent mixture being in excess of 15 percent and not in excess of thirty percent, chilling the mixture to solidify the wax and separating the solidified wax, thereby obtaining a lubricating oil of high viscosity index and low pour point.

2. A method of producing a lubricating oil of high viscosity index and low pour point from a wax bearing mineral lubricating oil, which comprises extracting the wax bearing oil with a mixture of liquid sulphur dioxide and an aromatic hydrocarbon of the group consisting of benzo-l and its homologues in which the sulphur dioxide is in excess of 50 percent in order to obtain a raflinate'phase and an extract phase, separating the two phases from each other and adding to the raflinate phase additional liquid sulphur dioxide and said aromatic hydrocarbon in such amounts that the total solvent in the mixture equals at least the amount of rafiinate oil, the liquid sulphur dioxide in the solvent mixture being in excess of 15 percent and not in excess of 30 percent, chilling the mixture to solidify the wax and separating the solidified Wax, thereby obtaining a lubricating oil of high viscosity index and low pour point.

3. A method of producing a lubricating oil of high viscosity index and low pour point from a wax bearing mineral lubricating oil, which comprises extracting the wax bearing oil with a mixture of liquid sulphur dioxide and benzol in which the sulphur dioxide is in excess of 50 percent, in order to obtain a rafiinate phase and an extract phase, separating the two phases from each other and adding to the rafifinate phase additional liquid sulphur dioxide and benzol in such amounts that the total solvent in the mixture is not over twice the amount of the rafiinate oil, the liquid sulphur dioxide in the solvent mixture being in excess of 15 percent and not in excess of percent, chilling the mixture to solidify the wax and separating the solidified wax, thereby obtaining a lubricating oil of high viscosity index and low pour point.

4. A method of producing a lubricating oil of high viscosity index and low pour point from a wax bearing mineral lubricating oil, which comprises extracting the wax bearing oil with a mixture of liquid sulphur dioxide and an aromatic hydrocarbon of the group consisting of benzol and its homologues in which the sulphur dioxide is in excess of percent, in'order to obtain a raflinate phase and an extract phase, separating the two phases from each other and adding to: the raffinate phase additional liquid sulphur dioxidejand said aromatic hydrocarbon in such amounts that the total solvent in the mixture is not over three times the amount of raflinate oil, the liquid sulphur dioxide in the solvent mixture being in excess of 15 percent and not in excess of 30 percent, chilling the mixture to solidify the wax and separating the solidified wax, thereby obtaining a lubricating oil of high viscosity index and low pour point.

5. A method of producing a lubricating oil of high viscosity index and low pour point from a wax bearing mineral lubricating oil, which comprises extracting the wax bearing oil withv a mixture of liquid sulphur dioxide and benzol in which the sulphur dioxide is in excess of 50 percent, in order to obtain a raflinate phase and an extract phase, separating the two phases from each other and adding to the rafiinate phase additional liquid sulphur dioxids and :benzol in such amounts that the liquid sulphur dioxide in the solvent mixture is reduced to over 15 percent and not in excess of thirty percent, chilling the mixture to solidify the wax and separating the solidified wax, thereby obtaining a lubricating oil of high viscosity index and 10w pour point.

ERICH SAEGEBARTH. 

